I have legacy code that relies on pointers being 32-bit and want to use xCodeBuild to build that code from command line. This doesn\'t
You have to set the ONLY_ACTIVE_ARCH to NO if you want xcodebuild to use the ARCHS parameters. By passing these parameters, you can force the proper architecture.
xcodebuild ARCHS=i386 ONLY_ACTIVE_ARCH=NO -configuration Debug -workspace MyProject.xcworkspace -scheme MyLib
See this reference for details.